1. Field of the Invention
The present invention relates to a method for regenerating inorganic porous particles, a method for purifying water, and a continuous water purification device. The object thereof is to provide a method for regenerating inorganic porous particles, a method for purifying water, and a continuous water purification device, each of which can be applied as a water-recycling system even in special environment such as space environment by using compact equipment with no chemicals and safely removing ammonia and amines contained in water and water vapor.
Additionally, in the present specification, smaller pressure values means higher vacuum pressures, and larger pressure values means lower vacuum pressures.
2. Description of the Related Art
In recent years, manned space flights have been frequently carried out, using a spaceship such as a space shuttle, and also, construction of an international space station is planned.
In a case of astronauts staying in the space for a long period, the most serious problem is to ensure water. At the present, water necessary for astronauts"" lives is supplied with water as a byproduct of fuel cells and water replenished by launching from the earth. However, the supplement of water from fuel cells is restricted in terms of its amount, and it is difficult to replenish a large amount of water from the earth because the replenishment of water by launching from the earth costs about 2.5 million yen per kg of water. For such reason, as space staying time is prolonged and the number of flight crew members is increased, ensuring water in space environment has become a serious problem.
At present, researches have been conducted in recycling by purifying water or urine which are discharged from space facilities to the space. As for such present recycling system, an apparatus using a reverse osmotic membrane method and membrane distillation method have been examined. However, with the reverse osmotic membrane method which has a low efficiency in removing impurities, there is a defect that an apparatus used for this method has to be enlarged because this method requires multi-processed treatment. Moreover, a risk of explosion is incurred because this method requires a high pressure. Thus, this method cannot be easily applied to special environment such as space facilities of which size is restricted and space environment.
Membrane distillation method using a porous hydrophobic membrane is quite different to pervaporation membrane method. The membrane distillation is a separation method based on vapor pressure difference, which is driving force for permeation of respective components. The vapor pressure difference, which is the driving force, is caused by the difference in temperatures at both sides of the membrane. Since the membrane used in the membrane distillation method has pores, if the pressure in the permeation side thereof is reduced as in the pervaporation membrane method, components are not separated to permeate through the membrane. Weak points of the membrane distillation are as follows. First, the surface of a porous hydrophobic membrane turns hydrophilic by running for a long time so that liquid in its original condition becomes to permeate through the membrane. Also, on the basis of the module structure of the membrane, since high temperature and low temperature sections become close to each other at both sides of the membrane, the module structure becomes complicated and thus, it becomes difficult to make the structure light in weight. Further, permeation flow rate is small. For these reasons, this method cannot be easily applied in space facilities which size is restricted or in space environment.
The present inventors have researched a method for recycling waste water, urine or the like, which can be used in a restricted space in space facilities, by use of a simple device with no chemicals.
First, the present inventors have examined a method of using inorganic porous particles such as silica gel particles as a method for separating impurities which has been hitherto used. This method is a method having high separating ability. However, this method has a problem that for long-term use thereof regeneration-treatment is essential because long term use of this method causes a decrease in adsorptivity. As for regeneration of the inorganic porous particles, it is general to use a solvent, however, in space environment, no regenerating method using a chemical can be applied because the use of the chemical (the solvent) causes a discharge of new waste. Also, as a result of the present inventors"" eager investigations, they have decided to research on regenerating inorganic porous particles without using chemicals.
As a membrane separation method, there is a pervaporation method which is different from the reverse osmotic membrane method and the like without no conditions incurring a risk, such as a pressurization condition, as a separation method of membranes which can make an apparatus therefor small in size. This method together with the above-mentioned problems has been studied at the same time. This pervaporation method is a separation method involving phase-changes wherein feeding side (primary side) thereof is liquid and the permeation side (secondary side) thereof is gas. Any conventional membrane method has a problem that substances, which are slightly different in their molecular weights or boiling points and have similar characteristics, for example, water and ammonia or amines, cannot be separated. Therefore, it is necessary to solve the problems that similar substances, such as water and ammonia or the like, are separated and simultaneously make good use of an advantage of the pervaporation method of which apparatus is small in size.
The present invention has been invented for solving many problems such as the above-mentioned, and the invention is a method for regenerating inorganic porous particles adsorbing at least ammonia and/or amines, and it relates to the method for regenerating inorganic porous particles, which is characterized in that the inorganic porous particles are heated to 100-200xc2x0 C. under a reduced pressure of 10 Pa or less to remove adsorbed products such as ammonia and/or amines.
The invention is a method for purifying water containing at least ammonia and/or amines as impurities by pervaporation method and it relates to the method for purifying water which is characterized in that a dense membrane having cationic groups is used as a permeable membrane so as to suppress permeation of the impurities such as ammonia and/or amines and further cause water to permeate preferentially through the membrane.
The invention is a method for purifying water containing at least ammonia and/or amines as impurities by pervaporation method, and it relates to the method for purifying water, which is characterized in that a composite membrane wherein a hydrophilic membrane is layered on a surface of a hydrophobic porous membrane is used as a permeable membrane so as to suppress permeation of water and further cause the impurities such as ammonia and/or amines to permeate preferentially through the membrane.
The invention is a method for purifying water containing at least ammonia and/or amines as impurities by pervaporation method, and it relates to a method for purifying water, which is characterized in that a dense membrane having cationic groups is used as a permeable membrane so as to suppress permeation of the impurities such as ammonia and/or the amines, and further the impurities that have permeated through said permeable membrane are adsorbed and removed by use of inorganic porous particles.
The invention is a method for purifying water containing at least ammonia and/or amines as impurities by pervaporation method, and it relates to the method for purifying water, which is characterized in that a composite membrane layered on a surface of a hydrophobic porous membrane is used as a permeable membrane so as to cause the impurities such as ammonia and/or amines to permeate preferentially through the membrane, and further the impurities that have not permeated through said permeable membrane are adsorbed and removed by use of inorganic porous particles.
The invention is a method for purifying water containing at least ammonia and/or amines as impurities by pervaporation method, and it relates to the method for purifying water, which is characterized in that a composite membrane wherein a hydrophilic membrane is layered on a surface of a hydrophobic porous membrane is used as a permeable membrane so as to cause the impurities such as ammonia and/or amines to permeate preferentially through the composite membrane; fraction that has not permeated through said composite membrane is further subjected to the pervaporation using a dense membrane having cationic groups so as to suppress permeation of the impurities such as ammonia and/or amines and cause water to permeate preferentially through the dense membrane; and the impurities that have permeated through the dense membrane having said cationic groups are adsorbed and removed by use of inorganic porous particles.
The invention is a method for purifying water, and it relates to the method for purifying water, which is characterized in that the inorganic porous particles adsorbing the impurities such as ammonia and/or amines are heated to 100-200xc2x0 C. under a reduced pressure of 10 Pa or less, to remove the adsorbed products such as ammonia and/or amines.
The invention is a continuous water purification apparatus containing at least ammonia and/or amines as impurities, which comprises a pervaporation apparatus and two or more impurity-adsorbing apparatuses wherein a permeable membrane of said pervaporation apparatus comprises a dense membrane having cationic groups, a regenerating apparatus comprising a heating means and a pressure-reducing means is disposed in each of the impurity-adsorbing apparatuses, and it relates to the continuous water purification apparatus, which is characterized in that a permeation side of the pervaporation apparatus is connected to the impurity-adsorbing apparatuses through vapor-sending tubes to which directional controlling valves are fitted, respectively.
The invention is a continuous water purification apparatus containing at least ammonia and/or amines as impurities, which comprises first and second pervaporation apparatuses and two or more impurity-adsorbing apparatus, and it relates to the continuous water purification apparatus which is characterized in that a permeable membrane of said first pervaporation apparatus is comprised of a composite membrane in which a hydrophilic membrane is layered on a surface of a hydrophobic porous membrane, a permeable membrane of said second pervaporation apparatus is comprised of a dense membrane having cationic groups, a supplying side of said first pervaporation apparatus is connected to a supplying side of said second pervaporation apparatus so that fraction that has not permeated through the permeable membrane of the first pervaporation apparatus is supplied to the supplying side of the second pervaporation apparatus, a regenerating apparatus comprising a heating means and a pressure-reducing means is disposed in each of said impurity-adsorbing apparatuses, and a permeation side of said second pervaporation apparatus is connected to the impurity-adsorbing apparatuses through vapor-sending tubes to which directional controlling valves are fitted, respectively.